Nuclear transfer of adult and genetically modified fetal cells of the rat.

The present study examines the handling, activation, and micromanipulation of rat eggs in an attempt to produce live young using nuclear transfer (NT) of adult and genetically modified rat fetal cells. Mature rat eggs cultured in calcium-free medium showed reduced rates (24%) of chromosomal dispersion ("spontaneous activation" characteristic of this species) compared with eggs cultured in calcium-containing medium (47%), but failed to survive micromanipulation procedures. High rates of parthenogenetic cleavage were obtained with chemical activation using ethanol/cycloheximide (65%) compared with other standard chemical activation methods (4-28%).

Crystallization of the first three domains of the human insulin-like growth factor-1 receptor.

The insulin-like growth factor-1 receptor (IGF-1R) is a tyrosine kinase receptor of central importance in cell proliferation. A fragment (residues 1-462) comprising the L1-cysteine rich-L2 domains of the human IGF-1R ectodomain has been overexpressed in glycosylation-deficient Lec8 cells and has been affinity-purified via a c-myc tag followed by gel filtration. The fragment was recognized by two anti-IGF-1R monoclonal antibodies, 24-31 and 24-60, but showed no detectable binding of IGF-1 or IGF-2.

Insulin-responsive tissues contain the core complex protein SNAP-25 (synaptosomal-associated protein 25) A and B isoforms in addition to syntaxin 4 and synaptobrevins 1 and 2.

SNAP-25 (synaptosomal-associated protein 25), syntaxin and synaptobrevin are the three SNARE [soluble NSF attachment protein receptor (where NSF = N-ethylmaleimide-sensitive fusion protein)] proteins that form the core complex involved in synaptic vesicle docking and subsequent fusion with the target membrane. The present study is aimed at understanding the mechanisms of fusion of vesicles carrying glucose transporter proteins with the plasma membrane in human insulin-responsive tissues. It describes the isolation and characterization of cDNA molecules encoding SNAP-25 A and B isoforms, syntaxin 4 and synaptobrevins (also known as vehicle-associated membrane proteins) from two major human insulin-responsive tissues, skeletal muscle and fat.

Purification and properties of insulin receptor ectodomain from large-scale mammalian cell culture.

Ectodomain of the exon 11+ form of the human insulin receptor (hIR) was expressed in the mammalian cell secretion vector pEE6.HCMV-GS, containing the glutamine synthetase gene. Following transfection of the hIR ectodomain gene into Chinese hamster ovary (CHO-K1) cells, clones were isolated by selecting for glutamine synthetase expression with methionine sulphoximine.

Characterization of the mRNA encoding a proline-rich 37-kilodalton glycoprotein from the excretory-secretory products of Trichostrongylus colubriformis.

A glycoprotein, with apparent molecular weight in SDS-polyacrylamide gels of 37 kDa, has been isolated from the excretory-secretory (ES) products of the adult stage of Trichostrongylus colubriformis, a parasitic nematode. This protein is the major ES product recognized in immunoblots by lymph from a naturally infected sheep. A synthetic oligonucleotide, based on peptide sequence data from a digest of the purified protein was used to successfully screen a cDNA library.